Produce manager Nate Codina arranges a display of Rocky Ford cantaloupes at a Kings Soopers market in Denver last week. The new crop is out, just as health officials confirm a new strain linked to last year's deadly listeria outbreak.

A previously unidentified strain of listeria from last year’s deadly cantaloupe outbreak has been linked to the death of a 75-year-old Montana man, even as the new crop of Colorado melons fills store shelves.

The new strain was collected from cut cantaloupe in a home refrigerator last September, at the start of the listeria outbreak that eventually sickened 146 people and led to at least 30 deaths and one miscarriage. But Colorado health officials didn’t send the sample to federal officials for 10 months because it didn’t match strains from any known victims in that state.

“We didn’t look more broadly,” said Alicia Cronquist, an epidemiologist with the Colorado Department of Public Health and Environment.

When they finally did send it to the federal PulseNet monitoring program last month, it turned out to be identical to a rare strain of listeria detected in a Montana victim who died in January.

That increases the number of strains in the 28-state outbreak to five, up from the four strains responsible for most of the illnesses, said Dr. Benjamin Silk, an epidemiologist at the Centers for Disease Control and Prevention.

It also adds the elderly Bozeman man to the CDC’s roster of cases, bringing the tally to 147, though it’s not yet clear whether his death can be counted in the total.

“We know that the patient had the outbreak strain,” said Silk, who confirmed that the man ate contaminated cantaloupe. “What they’re looking into now is whether the cause of death was from the listeria infection.”

Montana health officials should learn this week whether listeria killed the man outright or whether another disease or illness was responsible, said Jim Murphy, chief of the state’s communicable disease bureau.

Rocky Ford cantaloupes back in storesThe first cantaloupes from Colorado’s famed Rocky Ford growing region have just appeared in local produce aisles last week after safety upgrades that totaled between $800,000 and $1 million, said spokeswoman Diane Mulligan, who represents a coalition of 15 area growers.

“The cantaloupe hit the shelves on Friday,” said Mulligan, noting that King Soopers grocery stores were swamped by demand. “I can’t get any.”

Those growers are hoping to overcome the damage caused by Jensen Farms, the Holly, Colo., grower responsible for the outbreak, one of the deadliest in U.S. history. Faulty growing, processing and storage conditions and dirty equipment led to the problems, government health officials concluded.

The new safety measures adopted by the Rocky Ford Growers Association include specialized washing, disinfectant and cooling procedures, as well as tracking that monitors the melons from seed to store, Mulligan said.

“They’ve basically taken the utmost safety precautions and are adhering to the stringent processes that are out there,” she added.

Delayed reporting of the new strain of listeria could have missed other victims, Cronquist, the Colorado epidemiologist, said.

“There’s always a concern that there were others who were sickened by this strain who were not identified,” she said.

The move was prompted only after a food safety lawyer requested state health records related to another cantaloupe victim. Patti Waller, an epidemiologist who works for Marler Clark, the Seattle firm, brought the strain to the lab’s attention, Cronquist confirmed. The situation was first reported in Marler Clark's Food Safety News blog.

Waller had been investigating the case of Isaak Margolin, a 97-year-old Colorado man who was sickened by one of the four previously identified outbreak strains of listeria last fall, health records showed. Samples of whole cantaloupe and cut cantaloupe from Margolin’s refrigerator included two other strains confirmed in the outbreak.

But one additional strain of listeria was isolated from cut cantaloupe in Margolin’s refrigerator -- and later identified in the Montana man who died.

Colorado officials have changed their protocol for sending samples to the CDC in the wake of the incident, said Cronquist.

“Our lab will post all isolates, not just those in confirmed victims,” she said.